I sometimes do odd jobs in a church, including rehanging doors. The church is 400 years old, I think the doors are a lot newer but still 100-150 years old.
Getting the hinges off is not easy (to say the least) but I at least want to help whoever is doing my job in another 150 years. So I pre-bore and lubricate the screws. My father was a chippie and used vaseline, but a fellow odd-jobber said he uses soap.
What is the best lubricant? soap, vaseline or something else?
Bee's wax. Time honored and true. It comes in small blocks, just rub the screw threads across the block. As a union carpenter on a major industrial job, I learned this from a old timer fifty years ago and still use it myself. I mostly use it to more easily insert screws but I suppose it would lead to easier extraction as well.
I'd avoid oils for reasons cited by others.
If you're referring to the actual screws used to hold the hinge onto the jamb, and holding the door onto the hinge, a possible solution might be to take all the hinges off the doors and the jambs, and inject JB-Weld or similar into all the screw holes. Make sure it is really packed in there. Wait for it to fully cure, then run an appropriately sized drill and tap through it.
Tapping machine screw threads into the jambs and doors will let you use machine screws that are much better and easier to take out and put back in many times over.
What is the best lubricant? soap, vaseline or something else?
I'm not sure anyone can say. I've read recommendations for both soap and Vaseline as lubricants from multiple sources spanning over 100 years, indicating they were both used widely In addition, and in no particular order: linseed oil, candle wax, paste wax and a few other things that aren't commonly found in workshops today including tallow or mutton fat and lard.
I suppose you should find out whichever gives the best lubrication in a side-by-side comparison and use that but my suspicion is that most of the commonly recommended lubricants for wood screws work about the same.
Note: lubrication of screws used on show surfaces should be done with restraint as there's a risk of staining the wood around the screw hole if too much of an oily lubricant is used. Also if you're finishing after the screws are driven home any grease, wax or oil that gets on the surface can cause problems when you apply the finish, so some discretion is advised.
My tradition, going back three or four generations, is: soap. I keep the tag ends of bath bar soap in a ziplock with a tiny bit of water and wipe wood screw threads across the soap before inserting them in the tapered predrilled holes. It's most helpful in hardwoods.
But I'm not dogmatic, wax would work I'm pretty sure and boiled Linseed oil sounds interesting.
Unless you can guaranty that you can insert a machine screw insert exactly in the right place and perpendicular to the surface I would avoid them. Good idea when you can use a drill press, though.
Please no JB weld. If you do decide you must use an epoxy use WEST, System 3 or equivalent, and fill with cabosil, although no epoxy will make it easier for the next volunteer carpenter. If there is damage scarf in a new piece of wood, then you can use an epoxy, but PVA would probably work just as well here.
